1. Field of the Invention
The subject matter of this invention is related generally to motor contactors and more specifically to the kick-out spring system of a vacuum contactor.
2. Description of the Prior Art
Motor contactors are known. They are electrical devices which are used to start and stop electrical motors in response to signals from pushbuttons, limit switches and a variety of pilot devices. Contactors in general have as part thereof a circuit interrupting device. In the past, air brake circuit interrupting devices have been utilized which interrupt electrical current in an arc chute in air. More recently, vacuum circuit interrupting devices have been utilized to replace the air brake devices. The vacuum devices have a number of desirable features, one of which is relatively small contact separation when compared with the contact separation required in an air brake device. This means that smaller and more compact systems may be utilized with the attendant space savings associated therewith for any given voltage withstand rating when compared with the air brake type interrupter device. The main difference between vacuum contactors and conventional air brake contactors is that the vacuum contactor interrupts electrical current inside a vacuum chamber instead of inside of an air arc chute. The vacuum chamber typically consists of an assembly of a sealed evacuated enclosure surrounding a first fixed electrical contact and a movable electrical contact the motion of which is provided through a gas-tight flexible metallic bellows. One of the interesting characteristics of a vacuum interrupter is that the atmospheric pressure which surrounds the external portion thereof operates against the internal vacuum through the bellows thus tending to maintain the contacts in a closed state. In order to overcome this, a strong kick-out spring is utilized to assist in opening closed contacts and in keeping the open contacts in an open state. Typically, a vacuum interrupter is closed by utilizing an electromagnet to move an armature which is mechanically interlinked with the movable contact inside the vacuum chamber to cause the contact to abut or close the stationary contact. When the electromagnetic energy is removed from the electromagnet, the kick-out spring overcomes the atmospheric force and opens the contacts and keeps them open. Examples of prior art vacuum contactors may be found in the following descriptive bulletins: "Westinghouse Type SJO Vacuum Contactor", IL16-200-33 published by the Westinghouse Electric Corporation Control Division, Asheville, N.C., U.S.A. 28813, dated October 1982 and "Westinghouse Type SJA Vacuum Contactor", IL16-200-32 published by the Westinghouse Electric Corporation Control Division, Asheville, N.C., U.S.A. 28813, published November 1982. By reference to the fourth full paragraph of the left column of page 2 of the "SJA" bulletin, for example, it can be seen that the kick-out spring must be removed before the electromagnetic coil can be changed, for example. Removal of the kick-out springs of necessity requires readjustment thereof when reinstalled. It would be advantageous if electrical contactor apparatus could be found which utilize an adjusted kick-out spring and which could be disassembled without affecting the adjustment on the kick-out spring.